Method for selectively performing local and radial peripheral stimulation

ABSTRACT

A control system for use with a neurostimulator comprises a user interface for receiving an input from a user and a controller. The user interface has a first control and a second control. The controller is configured for, in response to actuating the first control, operating the neurostimulation control system in a PNFS programming mode, and for, in response to actuating the second control, operating the neurostimulation control system in a PNS programming mode. A method of providing therapy to a patient comprises initially conveying pulsed electrical current at a pulse width into a peripheral tissue region of the patient to create a side effect via stimulation of one of a nerve ending and neural axon, and subsequently conveying pulsed electrical current at an adjusted pulse width into the peripheral tissue region to create a therapeutic effect via stimulation of the other one of the nerve ending and neural axon.

RELATED APPLICATION DATA

The present application is a divisional application of U.S. patentapplication Ser. No. 13/197,949, now issued as U.S. Pat. No. 8,718,780,which claims the benefit under 35 U.S.C. §119 to U.S. Provisional PatentApplication Ser. No. 61/373,692, filed Aug. 13, 2010, which applicationsare all incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to tissue stimulation systems, and moreparticularly, to a system and method for peripherally stimulating nervetissue.

BACKGROUND OF THE INVENTION

Implantable neurostimulation systems have proven therapeutic in a widevariety of diseases and disorders. In recent investigations, PeripheralStimulation (PS) (i.e., stimulation of nerve tissue outside of thespinal cord and brain), which includes Peripheral Nerve FieldStimulation (PNFS) techniques that stimulate nerve tissue directly atthe symptomatic site of the disease or disorder (e.g., at the source ofpain), and Peripheral Nerve Stimulation (PNS) techniques that directlystimulate bundles of peripheral nerves that may not necessarily be atthe symptomatic site of the disease or disorder, has demonstratedefficacy in the treatment of chronic pain syndromes (e.g., painfulperipheral neuropathy (PN), post-herpetic neuralgia (PHN), fibromyalgiasyndrome (FMS), failed back surgery syndrome (FBSS), Arachnoiditis,occipital neuralgia, peripheral pelvic pain, cardiac pain, etc.) andincontinence, and a number of additional applications are currentlyunder investigation.

An implantable neurostimulation system, whether used in the context ofPS or another stimulation application, typically includes one or moreelectrode carrying stimulation leads, which are implanted at the desiredstimulation site. In PS, the stimulation lead(s) are implanted in thesubcutaneous tissues of a peripheral region, such as the lower backregion, cervical region, arm, or leg. The implantable neurostimulationsystem further includes a neurostimulator (e.g., an implantable pulsegenerator (IPG)) implanted within a tissue pocket remotely from thestimulation site, but coupled to the stimulation lead(s). Thus,electrical pulses can be delivered from the neurostimulator to thestimulation lead(s) to stimulate or activate a volume of neural tissue.In particular, electrical energy conveyed between at least one cathodicelectrode and at least one anodic electrodes creates an electricalfield, which when strong enough, depolarizes (or “stimulates”) theneurons beyond a threshold level, thereby inducing the firing of actionpotentials (APs) that propagate along the neural fibers.

Stimulation energy may be delivered to the electrodes during and afterthe lead placement process in order to verify that the electrodes arestimulating the target neural elements and to formulate the mosteffective stimulation regimen. The regimen will dictate which of theelectrodes are sourcing current pulses (anodes) and which of theelectrodes are sinking current pulses (cathodes) at any given time, aswell as the magnitude, duration, and rate of the current pulses. Thestimulation regimen will typically be one that provides stimulationenergy to all of the target tissue that must be stimulated in order toprovide the therapeutic benefit, yet minimizes the volume of non-targettissue that is stimulated. In the case of PS, such a therapeutic benefitis accompanied by “paresthesia,” i.e., a tingling sensation that iseffected by the electrical stimuli applied through the electrodes.

While PS has been generally useful in treating patients, there stillremain issues. For example, an electrical field applied to a particularperipheral region may not only stimulate nerve endings that innervate aregion local to the applied electrical field, but also stimulate neuralaxons that innervate tissue remote from the applied electrical field. Assuch, it is often difficult to selectively perform PNFS and PNS. Thatis, when PNFS is desired, PNS may inadvertently be performed instead ofor in addition to PNS, and when PNS is desired, PNFS may inadvertentlybe performed instead of or in addition to PNS.

There, thus, remains a need for an improved technique to selectivelyperform PNFS and PNS in a patient.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present inventions, aneurostimulation control system for use with a neurostimulator isprovided. The neurostimulation system comprises a user interfaceconfigured for receiving an input from a user. The interface has a firstcontrol and a second control, each of which may be, e.g., a graphicalicon. The neurostimulation control system further comprises a controllerconfigured for, in response to a single actuation of the first control,operating the neurostimulation control system in a peripheral nervefield stimulation (PNFS) programming mode, and for, in response to asingle actuation of the second control, operating the neurostimulationcontrol system in a peripheral nerve stimulation (PNS) programming mode.The user interface and controller may be contained within an externalcontrol device.

In one embodiment, the controller, when the neurostimulation controlsystem is in the PNFS mode, is configured for only allowing a user toprogram the neurostimulator to convey pulsed anodic stimulation currentat a pulse width below an upper limit (e.g., less than 700 μs), and whenthe neurostimulation control system is in the PNS mode, is configuredfor only allowing a user to program the neurostimulator to convey pulsedcathodic stimulation current at a pulse width above a lower limit (e.g.,greater than 500 μs).

In another embodiment, the controller, when the neurostimulation controlsystem is in the PNFS mode, is configured for automatically programmingthe neurostimulator to convey pulsed anodic stimulation current at afirst pulse width (e.g., a value less than 700 μs), and when theneurostimulation control system is in the PNS mode, is configured forautomatically programming the neurostimulation to convey pulsed cathodicstimulation current at a second pulse width (e.g., a value greater than500 μs).

In accordance with another aspect of the present inventions, a method ofproviding therapy (e.g., a reduction in or elimination of pain) to apatient is provided. The method comprises initially conveying pulsedelectrical current at a pulse amplitude and a pulse width into aperipheral tissue region of the patient, whereby one of a nerve endingis stimulated to create a side effect local to the peripheral neuraltissue region and a neural axon is stimulated to create a side effectremote from the peripheral neural tissue region. The method furthercomprises adjusting the pulse width, and subsequently conveying pulsedelectrical current at the adjusted pulse width into the peripheraltissue region of the patient, whereby only one of the other of the nerveending is stimulated to create a therapeutic effect local to theperipheral neural tissue region and the neural axon is stimulated tocreate a therapeutic effect remote from the peripheral neural tissueregion. In one method, both the initially and subsequently conveyedpulsed electrical current have the same pulse amplitude. Another methodfurther comprises adjusting the pulse amplitude, wherein the pulsedelectrical current is subsequently conveyed at the adjusted pulseamplitude into the peripheral region of the patient.

If the nerve ending is stimulated to create the side effect, and theneural axon is stimulated to create the therapeutic effect, thesubsequently conveyed pulsed electrical current is preferably cathodic.In this case, the pulse width may be adjusted by increasing the pulsewidth (e.g., to a value greater than 500 μs), and if the initiallyconveyed pulsed electrical current is anodic, the polarity of the pulsedelectrical current is switched from anodic to cathodic. If the neuralaxon is stimulated to create the side effect, and the nerve ending isstimulated to create the therapeutic effect, the subsequently conveyedpulsed electrical current is preferably anodic. In this case, the pulsewidth may be adjusted by decreasing the pulse width (e.g., to a valueless than 700 μs), and if the initially conveyed pulsed electricalcurrent is cathodic, the polarity of the pulsed electrical current isswitched from cathodic to anodic.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is plan view of one embodiment of a peripheral tissue stimulationsystem arranged in accordance with the present inventions;

FIG. 2 is a perspective view of a microstimulator used in the peripheralstimulation system of FIG. 1;

FIG. 3 is a block diagram of the internal components of themicrostimulator of FIG. 2;

FIG. 4 is a plan view of a remote control that can be used in theperipheral tissue stimulation system of FIG. 1;

FIG. 5 is a block diagram of the internal componentry of the remotecontrol of FIG. 4;

FIG. 6 is a block diagram of the components of a clinician programmerthat can be used in the peripheral tissue stimulation system of FIG. 1;

FIG. 7 is a plan view of a programming screen created by the clinicianprogrammer of FIG. 6 for programming the microstimulator of FIG. 2;

FIG. 8a is a bar graph illustrating the local and remote sensationsexperienced by five subjects in accordance with different pulse widthsof applied cathodic electrical current;

FIG. 8b is a bar graph illustrating the local and remote sensationsexperienced by five subjects in accordance with different pulse widthsof applied anodic electrical current;

FIG. 9a is a diagram of strength-duration curves for the stimulation ofnerve endings and neural axons generated from the bar graph of FIG. 8a ;and

FIG. 9b is a diagram of strength-duration curves for the stimulation ofnerve endings and neural axons generated from the bar graph of FIG. 8 b.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Turning first to FIG. 1, an exemplary neurostimulation system 10 is usedto selectively perform Peripheral Nerve Field Stimulation (PNFS) andPeripheral Nerve Stimulation (PNS). The system 10 generally includes aneurostimulator in the form of a microstimulator 12, external controldevices, and in particular a handheld remote controller (RC) 14 and aclinician's programmer (CP) 16, and an external charger 18.

The microstimulator 12 includes pulse generation circuitry that deliverselectrical stimulation energy in the form of a pulsed electricalwaveform (i.e., a temporal series of electrical pulses) to tissue inwhich the microstimulator 12 is implanted in accordance with a set ofstimulation parameters. As shown in FIG. 1, the microstimulator 12 issubcutaneously implanted within a peripheral region 45 (e.g., an arm,leg, lower back, neck, etc.) of a patient using suitable means, such asa needle. The preferred placement of the microstimulator 12 is justbelow the cutaneous layer 46 of the patient. As there shown, themicrostimulator 12 is located adjacent one or more nerve endings 47 thatprovide sensory information local to the peripheral region 44 and one ormore neural axons 48 that provide afferent or efferent information to orfrom a region remote from the peripheral region 44.

The RC 14 may be used to telemetrically control the microstimulator 12via a bi-directional RF communications link 20. Such control allows themicrostimulator 12 to be turned on or off and to be programmed withdifferent stimulation parameters. The microstimulator 12 may also beoperated to modify the programmed stimulation parameters to activelycontrol the characteristics of the electrical stimulation energy outputby the microstimulator 12.

The CP 16 provides clinician detailed stimulation parameters forprogramming the microstimulator 12 in the operating room and infollow-up sessions. The CP 16 may perform this function by indirectlycommunicating with the microstimulator 12 through the RC 14 via an IRcommunications link 22. Alternatively, the CP 16 may directlycommunicate with the microstimulator 12 via an RF communications link(not shown). The clinician detailed stimulation parameters provided bythe CP 16 are also used to program the RC 14, so that the stimulationparameters can be subsequently modified by operation of the RC 14 in astand-alone mode (i.e., without the assistance of the CP 16).

The external charger 18 is a portable device used to transcutaneouslycharge the microstimulator 12 via an inductive link 24. For purposes ofbrevity, the details of the external charger 18 will not be describedherein. Details of exemplary embodiments of external chargers aredisclosed in U.S. Pat. No. 6,895,280, which has been previouslyincorporated herein by reference. Once the microstimulator 12 has beenprogrammed, and its power source has been charged by the externalcharger 18 or otherwise replenished, the microstimulator 12 may functionas programmed without the RC 14 or CP 16 being present.

Turning to FIGS. 2 and 3, the microstimulator 12 is designed tostimulate tissue that is local to its implantation site. Preferably, themicrostimulator 12 is small enough to be implanted almost anywhere inthe human body for treatment of a wide variety of diseases anddisorders. For example, the microstimulator 12 may have a length l inthe range of 26-30 mm, a width w in the range of 6.5-8 mm, and athickness t in the range of 3.5-5 mm. The microstimulator 12 isgenerally rectangular, although it should be understood that themicrostimulator 12 may alternatively be cylindrical, elongated oval,square, or any other suitable shape.

To this end, the microstimulator 12 comprises a circuit module 26, anenergy storage module 28, a feed-through module 30, and a plurality ofexterior surface electrodes 32. The energy storage module 28 is coupledon one end to the circuit module 26 and on the other end to thefeed-through module 30.

The circuit module 26 includes an interior cavity that houses aprogrammable memory 34, active electrical circuitry 36, andtelemetry/charging coil 38. The active electrical circuitry 36 withinthe circuit module 26 is coupled to the electrodes 32 via a number offeed-throughs 40 in the feed-through assembly 30 and a plurality ofrespective electrical traces 42. Any other components of themicrostimulator 12 that may best serve a particular application may alsobe housed within the circuit module 26.

The energy storage module 28 contains an energy storage device 44, suchas a battery, is configured to output a voltage used to supply thevarious components within the microstimulator 12 with power. The battery44 also provides power for any stimulation current applied by themicrostimulator 12 to a stimulation site. The battery 44 may be aprimary battery, a rechargeable battery, a capacitor, or any othersuitable power source.

The electrodes 32 (labeled E₁-E_(N)) are configured to apply theelectrical pulsed stimulation current to the stimulation site. Asdepicted in FIG. 3, there may be any number of electrodes 32 as bestserves a particular application. In some examples, one or more of theelectrodes 32 may be designated as stimulating electrodes and one of theelectrodes 32 may be designated as an indifferent electrode used tocomplete one or more stimulation circuits. Any of the electrodes 32 maybe configured as anodes or cathodes and the polarity of each electrode32 may be reprogrammed. In an alternative embodiment, an electrodecarrying lead (not shown) may be coupled to the microstimulator 12 inaddition to or as an alternative to the electrodes 32.

The programmable memory 34 is used for storing one or more sets of data,for example, electrical stimulation parameters. The programmable memory34 allows a patient, clinician, or other user of the microstimulator 12to adjust the electrical stimulation parameters to levels that are safeand efficacious for a particular medical condition and/or for aparticular patient. The electrical stimulation parameters may controlvarious parameters of the stimulation current applied to the stimulationsite including, but not limited to, electrode polarity, pulse amplitude,pulse rate, pulse width, burst pattern (e.g., burst on time and burstoff time), duty cycle or burst repeat interval, ramp on time and rampoff time of the pulsed stimulation current that is applied to thestimulation site. The programmable memory 34 may be any type of memoryunit such as, but not limited to, random access memory (RAM), static RAM(SRAM), a hard drive, or the like.

The active electrical circuitry 36 is configured for generating pulsedelectrical stimulation current that is delivered to the stimulation sitevia the electrodes 32. The electrical circuitry 36 may be configured toproduce monopolar or multipolar stimulation. The electrical circuitry 36may include one or more processors (not shown) configured for decodingthe stimulation parameter information stored in the programmable memory34 and generating the corresponding pulsed electrical stimulationcurrent. In some embodiments, the microstimulator 12 has at least fourchannels and drives up to sixteen electrodes or more. The activeelectrical circuitry 36 may include additional circuitry such ascapacitors, integrated circuits, resistors, coils, and the likeconfigured to perform a variety of functions as best serves a particularapplication.

The telemetry/charging coil 38 is configured for transcutaneouslyreceiving data from and/or transmitting data to an external controldevice, such as the RC 14 or CP 16, and receiving power from theexternal charger 18 that is stored in the battery 40. In the illustratedembodiment, such data and power is transmitted and/or received viaelectromagnetic energy (also referred to as a radio frequency (RF)field).

Further details discussing microstimulators are disclosed in U.S. patentapplication Ser. No. 10/178,011, entitled “Implantable Microstimulatorswith Programmable Multielectrode Configuration and Uses Thereof,” andU.S. patent application Ser. No. 11/280,620, entitled “ImplantableStimulator,” which are expressly incorporated herein by reference. Inalternative embodiments, an implantable pulse generator (IPG) with oneor more attached neurostimulation lead (not shown) may be used in placeof the microstimulator, as disclosed in U.S. Pat. No. 6,516,227, U.S.Patent Publication No. 2003/0139781, and U.S. patent application Ser.No. 11/138,632, entitled “Low Power Loss Current Digital-to-AnalogConverter Used in an Implantable Pulse Generator,” which are expresslyincorporated herein by reference.

It should be noted that rather than a microstimulator or IPG, theneurostimulation system 10 may alternatively utilize a neurostimulatorin the form of an implantable receiver-stimulator (not shown). In thiscase, the power source, e.g., a battery, for powering the implantedreceiver, as well as control circuitry to command thereceiver-stimulator, will be contained in an external controllerinductively coupled to the receiver-stimulator via an electromagneticlink. Data/power signals are transcutaneously coupled from acable-connected transmission coil placed over the implantedreceiver-stimulator. The implanted receiver-stimulator receives thesignal and generates the stimulation in accordance with the controlsignals.

Referring now to FIG. 4, one exemplary embodiment of an RC 14 will nowbe described. As previously discussed, the RC 14 is capable ofcommunicating with the microstimulator 12 or CP 16. The RC 14 comprisesa casing 50, which houses internal componentry (including a printedcircuit board (PCB)), and a lighted display screen 52 and button pad 54carried by the exterior of the casing 50. In the illustrated embodiment,the display screen 52 is a lighted flat panel display screen, and thebutton pad 54 comprises a membrane switch with metal domes positionedover a flex circuit, and a keypad connector connected directly to a PCB.In an optional embodiment, the display screen 52 has touchscreencapabilities. The button pad 54 includes a multitude of buttons 56, 58,60, and 62, which allow the microstimulator 12 to be turned ON and OFF,provide for the adjustment or setting of stimulation parameters withinthe microstimulator 12, and provide for selection between screens.

In the illustrated embodiment, the button 56 serves as an ON/OFF buttonthat can be actuated to turn the microstimulator 12 ON and OFF. Thebutton 58 serves as a select button that allows the RC 14 to switchbetween screen displays and/or parameters. The buttons 60 and 62 serveas up/down buttons that can be actuated to increment or decrement any ofstimulation parameters of the pulse generated by the microstimulator 12,including pulse amplitude, pulse width, and pulse rate. For example, theselection button 58 can be actuated to place the RC 14 in a “PulseAmplitude Adjustment Mode,” during which the pulse amplitude can beadjusted via the up/down buttons 60, 62, a “Pulse Width AdjustmentMode,” during which the pulse width can be adjusted via the up/downbuttons 60, 62, and a “Pulse Rate Adjustment Mode,” during which thepulse rate can be adjusted via the up/down buttons 60, 62.Alternatively, dedicated up/down buttons can be provided for eachstimulation parameter. Rather than using up/down buttons, any other typeof actuator, such as a dial, slider bar, or keypad, can be used toincrement or decrement the stimulation parameters. Further details ofthe functionality and internal componentry of the RC 14 are disclosed inU.S. Pat. No. 6,895,280, which has previously been incorporated hereinby reference.

Referring to FIG. 5, the internal components of an exemplary RC 14 willnow be described. The RC 14 generally includes a processor 64 (e.g., amicrocontroller), memory 66 that stores an operating program forexecution by the processor 64, as well as stimulation parameter sets ina navigation table (described below), input/output circuitry, and inparticular, telemetry circuitry 68 for outputting stimulation parametersto the microstimulator 12 and receiving status information from themicrostimulator 12, and input/output circuitry 70 for receivingstimulation control signals from the button pad 54 and transmittingstatus information to the display screen 52 (shown in FIG. 4). As wellas controlling other functions of the RC 14, which will not be describedherein for purposes of brevity, the processor 64 generates newstimulation parameter sets in response to the user operation of thebutton pad 54. These new stimulation parameter sets would then betransmitted to the microstimulator 12 via the telemetry circuitry 68.Further details of the functionality and internal componentry of the RC14 are disclosed in U.S. Pat. No. 6,895,280, which has previously beenincorporated herein by reference.

As briefly discussed above, the CP 16 greatly simplifies the programmingof multiple electrode combinations, allowing the user (e.g., thephysician or clinician) to readily determine the desired stimulationparameters to be programmed into the microstimulator 12, as well as theRC 14. Thus, modification of the stimulation parameters in theprogrammable memory of the microstimulator 12 after implantation isperformed by a user using the CP 16, which can directly communicate withthe microstimulator 12 or indirectly communicate with themicrostimulator 12 via the RC 14.

As shown in FIG. 2, the overall appearance of the CP 16 is that of alaptop personal computer (PC), and in fact, may be implanted using a PCthat has been appropriately configured to include adirectional-programming device and programmed to perform the functionsdescribed herein. Thus, the programming methodologies can be performedby executing software instructions contained within the CP 16.Alternatively, such programming methodologies can be performed usingfirmware or hardware. In any event, the CP 16 may actively control thecharacteristics of the electrical stimulation generated by themicrostimulator 12 to allow the optimum stimulation parameters to bedetermined based on patient feedback and for subsequently programmingthe microstimulator 12 with the optimum stimulation parameters.

To allow the user to perform these functions, the CP 16 includes a mouse72, a keyboard 74, and a display screen 76 housed in a case 78. In theillustrated embodiment, the display screen 76 is a conventional screen.It is to be understood that in addition to, or in lieu of, the mouse 72,other directional programming devices may be used, such as a trackball,touchpad, or joystick, can be used. Alternatively, instead of beingconventional, the display screen 76 may be a digitizer screen, such astouchscreen) (not shown), may be used in conjunction with an active orpassive digitizer stylus/finger touch.

As shown in FIG. 6, the CP 16 generally includes a processor 80 (e.g., acentral processor unit (CPU)) and memory 82 that stores a stimulationprogramming package 84, which can be executed by the processor 80 toallow the user to program the microstimulator 12 and RC 14. The CP 16further includes output circuitry 86 (e.g., via the telemetry circuitryof the RC 14) for downloading stimulation parameters to themicrostimulator 12 and RC 14 and for uploading stimulation parametersalready stored in the memory 66 of the RC 14, via the telemetrycircuitry 68 of the RC 14.

Execution of the programming package 84 by the processor 80 provides amultitude of display screens (not shown) that can be navigated throughvia use of the mouse 72. These display screens allow the clinician to,among other functions, to select or enter patient profile information(e.g., name, birth date, patient identification, physician, diagnosis,and address), enter procedure information (e.g., programming/follow-up,implant trial system, implant IPG, implant IPG and lead(s), replace IPG,replace IPG and leads, replace or revise leads, explant, etc.), generatea pain map of the patient, define the configuration and orientation ofthe leads, initiate and control the electrical stimulation energy outputby the leads 12, and select and program the microstimulator 12 withstimulation parameters in both a surgical setting and a clinicalsetting. Further details discussing the above-described CP functions aredisclosed in U.S. patent application Ser. No. 12/501,282, entitled“System and Method for Converting Tissue Stimulation Programs in aFormat Usable by an Electrical Current Steering Navigator,” and U.S.patent application Ser. No. 12/614,942, entitled “System and Method forDetermining Appropriate Steering Tables for Distributing StimulationEnergy Among Multiple Neurostimulation Electrodes,” which are expresslyincorporated herein by reference.

An example of a programming screen 100 that can be generated by the CP16 is shown in FIG. 7. The programming screen 100 allows a user toperform automated stimulation parameter testing, manual stimulationparameter testing, and electrode combination selection functions.

The programming screen 100 includes various stimulation parameterentries that define the ranges of stimulation parameters to beautomatically tested. In particular, the programming screen includes apulse width entry 102 (expressed in microseconds (μs)), a pulse rateentry 104 (expressed in Hertz (Hz)), and a pulse amplitude entry 106(expressed in milliamperes (mA)). The user may enter a “begin” value andan “end” value for each stimulation parameter to be automaticallyadjusted. In one embodiment, only a single parameter (e.g., pulse widthentry 102) is highlighted to be auto-adjusted. The programming screen100 also includes a start button 108, which begins the automaticadjustment of the highlighted stimulation parameter from its “begin”value through a minimum increment to its “end” value, and a stop button100, which halts the automatic adjustment of the highlighted stimulationparameter. The programming screen 100 also includes a pacing control112, the left arrow of which can be clicked to decrease the speed of theparameter adjustment and the right arrow of which can be clicked toincrease the speed of the parameter adjustment.

The programming screen 100 also includes various stimulation parametercontrols that can be operated by the user to manually adjust stimulationparameters. In particular, the programming screen 100 includes a pulsewidth adjustment control 114 (expressed in microseconds (μs)), a pulserate adjustment control 116 (expressed in Hertz (Hz)), and a pulseamplitude adjustment control 118 (expressed in milliamperes (mA)). Eachcontrol includes a first arrow that can be clicked to decrease the valueof the respective stimulation parameter and a second arrow that can beclicked to increase the value of the respective stimulation parameter.The programming screen 100 also includes multipolar/monopolarstimulation selection control 120, which includes check boxes that canbe alternately clicked by the user to provide multipolar or monopolarstimulation.

The programming screen 100 also includes an electrode combinationcontrol 122 having arrows that can be clicked by the user to select oneof three different electrode combinations 1-3. Each of the electrodecombinations 1-3 can be conventionally created either manually; forexample, clicking on selected electrodes of a graphical electrode array(not shown) as anodes and cathodes and defining a percentage anodiccurrent or cathodic current for each selected electrode (e.g., turningoff electrode E1 as an anode, and turning on electrode E2 as an anode,and defining an anodic current for electrode E2), or automatically; forexample, by gradually shifting current between anodic ones of theelectrodes and/or gradually shifting current between cathodic ones ofthe electrodes via a directional device, such as a joystick or mouse(e.g., shifting anodic electrical current from electrode E1 to electrodeE2 in 5% increments).

The programming screen 100 also includes a peripheral stimulationselection control 124, which includes check boxes that can bealternately clicked by the user to selectively place the system 10between a PNFS mode, in which the microstimulator 12 can be operated orprogrammed to perform only PNFS, and a PNS mode, in which themicrostimulator 12 can be operated or programmed to perform only PNS. Inthe illustrated embodiment, the peripheral stimulation selection control124 is implemented as a graphical icon that can be clicked with a mouseor touched with a finger in the case of a touchscreen. Alternatively,the peripheral stimulation selection control 124 may be incorporatedinto the programming interface device as a button or key that is pressedwhen activated and then depressed when released, such as an Alt key. Anycontrol mechanism that programs the microstimulator 12 to operate ineither of the PNFS and PNS modes in response to a single actuation canbe utilized as the peripheral stimulation selection control 124. Theprogramming screen 100 further comprises a stimulation on/off control126 that can be alternately clicked to turn the stimulation on or off.

Significantly, the microstimulator 12 can be operated or programmed toperform PNFS or PNS by adjusting the pulse width and polarity of thepulsed stimulation current output by the microstimulator 12. Notably, ithas been discovered that by selecting the pulse width and polarity ofpulsed electrical current applied to a peripheral region, local nerveendings (the stimulation of which is associated with PNFS) and neuralaxons (the stimulation of which is associated with PNS) can beselectively activated.

In particular, an experiment was performed on five subjects during whicha stimulation electrode was used to transcutaneously stimulate aperipheral region adjacent the ulnar nerve of the five subjects whilethe pulse width and polarity of the stimulation current were adjusted.Notably, it is expected that the therapeutic effects of transcutaneousstimulation are similar to those of subcutaneous stimulation, and thus,the experimental results of the transcutaneous stimulation may beapplied to support conclusions involving subcutaneous stimulation.

During stimulation, the pulse width of the stimulation current was setat 50 μs, 100 μs, 200 μs, 500 μs, 700 μs, and 1000 μs for each of acathodic stimulation current and an anodic stimulation current, and eachsubject was requested to provide feedback for each setting as to whethera local sensation (resulting from the stimulation of nerve endings inthe elbow), which was defined as a sensation within 5 cm of thestimulation electrode, a remote sensation (resulting from thestimulation of the ulnar nerve), which was defined as a sensation withinthe hand, or both a local sensation and a remote sensation wasexperienced. For each pulse width setting, the amplitude of the currentwas increased from zero until the subject experienced a sensation fromthe stimulation. If a subject experienced only a local sensation or onlya remote sensation, the local sensation or the remote sensation wasquantified as 100%, and if the subject experienced both a localsensation and a remote sensation, each of the local and remotesensations was quantified as 50%. The data from the five subjects werethen averaged.

As can be seen from FIG. 8a , when cathodic electrical current was usedto stimulate the subjects, a pulse width of 500 μs or less yielded amixture of both a local sensation and a remote sensation, while a pulsewidth greater than 500 μs yielded only a remote sensation. The strengthduration curves illustrated in FIG. 9a , which represent the pulseamplitude and pulse width needed to respectively stimulate nerve endingsin the elbow region and the ulnar nerve, were generated from thecathodic electrical current stimulation experiment presented in FIG. 8a. As can be appreciated from a review of FIG. 9a , the separation of thestrength duration curves for the respective nerve endings and ulnarnerve is relatively large at relatively high pulse widths. As such,selectively between activation of the nerve endings and the ulnar nerveis relatively high at these relatively high pulse durations for cathodiccurrent stimulation. Furthermore, the strength duration curve for theulnar nerve has a lower threshold than that of the nerve endings atrelatively high pulse widths, and as such, the ulnar nerve will bestimulated before the nerve endings.

In contrast, as can be seen from FIG. 8b , when anodic electricalcurrent was used to stimulate the subjects, a pulse width of 700 μs orgreater yielded a mixture of both a local sensation and a remotesensation, while a pulse width less than 700 μs yielded only a localsensation. The strength duration curves illustrated in FIG. 9b , whichrepresent the pulse amplitude and pulse width needed to respectivelystimulate nerve endings in the elbow region and the ulnar nerve weregenerated from the anodic electrical current stimulation experimentpresented in FIG. 8b . As can be appreciated from a review of FIG. 9b ,the separation of the strength duration curves for the respective nerveendings and ulnar nerve is relatively large at relatively low pulsedurations. As such, selectively between activation of the nerve endingsand ulnar nerve is relatively low at these relatively high pulsedurations for anodic current stimulation. Furthermore, the strengthduration curve for the nerve endings has a lower threshold than that ofthe ulnar nerve at relatively low pulse widths, and as such, the nerveendings will be stimulated before the ulnar nerve.

Thus, from this, it can be gathered that polarity and pulse width of anapplied electrical stimulation current are critical parameters inselectively activating local nerve endings and neural axons for thepurposes of selectively performing PNFS and PNS.

To this end, when the microstimulator 12 is programmed by the CP 16 tooperate in the PNFS mode (i.e., by clicking the check box associatedwith the PNFS mode on the peripheral stimulation selection control 124),the microstimulator 12 may convey anodic electrical current through theselected stimulation electrode or electrodes at a pulse width less thana certain value (e.g., less than 700 μs). This can be accomplished byonly permitting the user to select certain electrodes as anodes andprogramming the microstimulator 12 within a relatively low pulse widthrange (e.g., using an upper limit value less than 700 μs) using thepulse width entry 102 or pulse width adjustment control 114.Alternatively, the CP 16 may automatically program the microstimulator12 to convey anodic stimulation current at a low pulse width.

In contrast, when the microstimulator 12 is programmed to operate in thePNS mode (i.e., by clicking the check box associated with the PNS modeon the peripheral stimulation selection control 124), themicrostimulator 12 is programmed, such that cathodic electrical currentis conveyed through the selected stimulation electrode or electrodes ata pulse width greater than a certain value (e.g., greater than 500 μs).This can be accomplished by only permitting the user to select certainelectrodes as cathodes and programming the microstimulator 12 within arelatively high pulse width range (e.g., using an lower limit valuegreater than 500 μs) using the pulse width entry 102 or pulse widthadjustment control 114. Alternatively, the CP 16 may automaticallyprogram the microstimulator 12 to convey cathodic stimulation current ata high pulse width.

PNFS and PNS can not only be selectively performed my placing the system10 in the PNFS programming mode or PNS programming mode via actuation ofthe peripheral stimulation selection control 124, but can also beselectively performed manually.

In particular, referring back to FIG. 1, if only PNFS is desired (inthis case, by stimulation of the nerve endings 47), anodic pulsedelectrical current is initially conveyed at a particular pulse widthinto the peripheral region 45 of the patient and the pulse amplitude isincreased until either a therapeutic effect, side effect, or both iscreated. Preferably, the pulse width is low enough (e.g., lower than 700μs), such that the initial conveyance of the anodic pulsed electricalcurrent results in only PNFS (in effect, creating a therapeutic effect(e.g., reduction or elimination of pain) local to the peripheral tissueregion 45 without creating a side effect remote from the peripheraltissue region 45). Because the optimum pulse width may not be known yet,it is possible that the initial conveyance of the anodic pulsedelectrical current may inadvertently result in PNS (in this case, bystimulation of the neural axon 48) in addition to the desired PNFS (ineffect, creating an undesirable side effect remote from the peripheraltissue region 45). In this case, anodic pulsed electrical current issubsequently conveyed into the peripheral region 45 of the patient, andwhile maintaining the pulse amplitude, the pulse width is decreaseduntil only PNFS is performed.

If only PNS is desired (in this case, by stimulation of the neural axon48), cathodic pulsed electrical current is initially conveyed at aparticular pulse width into the peripheral region 45 of the patient andthe pulse amplitude is increased until either a therapeutic effect, sideeffect, or both is created. Preferably, the pulse width is high enough(e.g., greater than 500 μs), such that the initial conveyance of thecathodic pulsed electrical current results in only PNS (in effect,creating a therapeutic effect (e.g., reduction or elimination of pain)remote from the peripheral tissue region 45 without creating a sideeffect local to the peripheral tissue region 45). Because the optimumpulse width may not be known yet, it is possible that the initialconveyance of the cathodic pulsed electrical current may inadvertentlyresult in PNFS (in this case, by stimulation of the nerve endings 47) inaddition to the desired PNS (in effect, creating an undesirable sideeffect local to the peripheral neural tissue region 45). In this case,cathodic pulsed electrical current is subsequently conveyed into theperipheral region 45 of the patient, and while maintaining the pulseamplitude, the pulse width is increased until only PNS is performed.

Although the foregoing techniques have been described as beingimplemented in the CP 16, it should be noted that this technique may bealternatively or additionally implemented in the RC 14.

Although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. A method of providing therapy to a patient,comprising: initially conveying cathodic pulsed electrical current at apulse amplitude and a pulse width into a peripheral tissue region of thepatient to initially stimulate a nerve ending to create a side effectlocal to the peripheral neural tissue region; increasing the pulsewidth; and subsequently conveying cathodic pulsed electrical current atthe increased pulse width into the peripheral tissue region of thepatient to only stimulate the neural axon to create a therapeutic effectremote from the peripheral neural tissue region.
 2. The method of claim1, wherein the both the initially and subsequently conveyed pulsedelectrical current have the same pulse amplitude.
 3. The method of claim1, wherein the pulse width is increased to a value greater than 500 μs.4. The method of claim 1, wherein the therapeutic effect is a reductionin or elimination of pain.
 5. The method of claim 1, further comprisingadjusting the pulse amplitude, wherein the pulsed electrical current issubsequently conveyed at the adjusted pulse amplitude into theperipheral region of the patient.
 6. A method of providing therapy to apatient, comprising: delivering cathodic pulsed electrical current intoa peripheral tissue region, including creating a side effect bydelivering the pulsed electrical current with a first pulse width, andthen only creating a therapeutic effect by delivering cathodic pulseelectrical current at a second pulse width that is greater than thefirst pulse width, wherein creating the side effect and then onlycreating the therapeutic effect includes creating the side effect localto the peripheral region and creating the therapeutic effect remote fromthe peripheral region.
 7. The method of claim 6, wherein creating theside effect includes stimulating a nerve ending in the peripheral tissueregion, and creating the therapeutic effect includes stimulating aneural axon in the peripheral neural tissue region.
 8. The method ofclaim 7, wherein the second pulse width is greater than 500 μs.
 9. Amethod of providing therapy to a patient, comprising: creating a sideeffect, including delivering cathodic pulsed electrical current with afirst pulse width into a peripheral tissue region, wherein creating theside effect includes creating the side effect local to a peripheralneural tissue region, including delivering the pulsed electrical currentto a nerve ending in the peripheral tissue region; and only creating atherapeutic effect subsequent to creating the side effect, includingdelivering cathodic pulsed electrical current with a second pulse widthinto the peripheral tissue region, the second pulse width being greaterthan the first pulse width, wherein creating the therapeutic effectincludes creating the therapeutic effect remote from the peripheraltissue region, including delivering the cathodic pulsed electricalcurrent with the second pulse width to the neural axon in the peripheraltissue region.